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    MIMO Toolbox

    For Use with MATLAB

    Oskar Vivero

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    About the toolbox

    The MIMO Toolbox is a collection of MATLABfunctions and a GUI. Its purpose is to

    complement the Control Toolbox for MATLABwith functions capable of handling the

    multivariable input-output scheme. All the results and examples except for example1.1.2.1 were obtained with the MIMO Toolbox and were corroborated with the

    bibliography.

    April, 2006

    Installation

    The installation is straightforward just copy the directory Mimotools and add the path

    to the MATLABsearch path.

    See path, in the MATLABdocumentation for more information.

    Requirements

    The MIMO Toolbox was created in Matlab 7.1 (R14) SP3, and requires the Symbolic

    and Control Toolboxes.

    Contact

    Oskar Vivero

    [email protected]

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    Contents

    1. Theory behind the functions

    1.1.SISO Systems

    1.1.1. Feedback Basic Concepts

    1.1.2. Nyquists Stability Criterion

    1.2.MIMO Systems

    1.2.1. Poles and Zeros of a MIMO System

    1.2.1.1. Smith-McMillan Transformation1.2.2. Stability of MIMO Systems

    1.2.2.1. Generalized Nyquists Stability Criterion

    1.2.3. Treating a MIMO System with SISO techniques

    1.2.3.1. Coupling degree and pairings of inputs and outputs

    1.2.3.2. Nyquists Arrays and Gershgorin Bands

    1.2.3.3. Relative Gain Array (RGA)

    1.2.3.4. Individual Channel Design (ICD)

    2.

    Function Reference

    2.1.The Symbolic Transfer Function

    2.2.

    Function Description

    2.2.1.

    tf2sym2.2.2. sym2tf

    2.2.3. ss2sym

    2.2.4. smform

    2.2.5. rga

    2.2.6. nyqmimo

    2.2.7. m_circles

    2.2.8. icdtool

    2.2.9. gershband

    2.2.10.arrowh

    3. References

    1

    1

    1

    2

    4

    4

    47

    7

    10

    10

    10

    11

    12

    14

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    19

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    21

    22

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    1. Theory behind the functions

    The aim of this chapter is to introduce the MIMO control theories so that one can

    understand both, the algorithm behind each function and its proper use. This chapter is

    only intended to provide a brief description of such theories and its recommended that

    the user refers to the bibliography listed at the end of this document.

    1.1 SISOSystems

    1.1.1 Feedback Basic Concepts

    Assuming a lineal process that is time-invariant whose behavior is defined by lineal

    differential equations with constant coefficients:

    1 2 1 2y a y a y b u b u

    + + = +

    where ( )y t is the output signal and ( )u t is the input signal, its possible to obtain a

    transfer function by applying the Laplaces Transform

    ( )

    ( ) ( )

    ( )

    ( )1 2

    2

    1 2

    Y s N s b s bG s

    U s D s s a s a

    += = =

    + +

    ( )

    ( )

    If 0 then is defined as a zero.

    If then is defined as a pole.

    Z Z Z

    P P P

    s s G s s

    s s G s s

    = =

    = =

    If ( )G s is rational, usually ( )D s determines the dynamic characteristics of the system,unless there exist cancellations between ( )N s and ( )D s .

    Let ( )H s and ( )G s be two transfer functions

    The stability of the system in a closed-loop configuration is given by ( ) ( )1 G s H s+ ifand only if there is no cancellation of instabilities. For any design, its possible to

    verify its stability by finding the singularities of ( )CLG s . If any of the singularities is

    located in2

    + or near the imaginary axis, its almost impossible to determine the

    modifications needed on either ( )G s or ( )H s to avoid the location of the singularities.

    The Nyquists stability criterion provides a tool for solving the problem

    ( ) ( )

    ( ) ( )1CL

    G sG s

    G s H s=

    +

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    1.1.2 Nyquists Stability Criterion

    The system in a closed-loop configuration is stable if and only if the trajectory of the

    Nyquist diagram of ( ) ( )G j H j from < < surrounds the point ( )1,0 in a

    counter-clockwise direction as much times as ( ) ( )G s H s has unstable poles.

    Theorem suppose that a function ( )f z is meromorphic in a simply connected domain

    D, and that C is a simple closed positively oriented contour in D such that ( )f z does

    not contain any singularities. Then

    ( )

    ( )

    '1

    2f f

    f zN dz Z P

    i f z= =

    where Nis the winding number,f

    Z is the number of zeros inside the contour andf

    P

    is the number of poles inside the contour.

    Example 1.1.2.1

    The image of the circle of radius 2 centered at the origin under ( ) 2f z z z= + is the

    curve ( ) ( ) ( ) ( ) ( )( ), 4cos 2 2cos , 4sin 2 2sing x y t t t t = + + . Note that the curve ( ),g x y winds up twice around the origin. We check this by computing

    ( )

    ( )

    0 1

    0 1

    2 2

    '1 ; Singulatiries at 0 and 1

    2

    2 1 2 1

    Res Res 2

    C

    z z

    f zN z z

    i f z

    z z

    N z z z z

    = = =

    + + = + = + +

    Having defined N, its important to define a useful contour for the stability analysis.

    Its possible to know from the root locus analysis and the time response that the

    unstable poles are at the right side of the S-plane. Since the zeros of the open loop

    system are the poles of the closed loop system, well focus on finding the unstable zeros

    through Nyquist frequency analysis. The contours that well consider are:

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    Example 1.1.2.2 [4] pp. 620

    Draw the Nyquist contour and diagram of ( )( )( ) ( )

    500

    1 3 10G s

    s s s=

    + + +

    Once the stability of a system has been defined through the Nyquists diagram, therobustness of the system can be defined by two quantities, the gain and phase margins.

    Gain margin ( )MG - the change of gain in open loop needed to obtain a phase shift at

    180 that turns the system unstable.

    Phase margin ( )M - the phase shift in open loop needed to turn the system unstable

    with a unit gain.

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    1.2 MIMOSystems

    The basic description of a multivariable system is through a transfer function matrix

    (TFM), whose elements ,i jg represent the i-est output with the j-est input. The

    elements,i j

    g are individual transfer functions.

    1.2.1 Poles and zeros of a MIMO system

    The poles and zeros of multivariable systems can be defined in several (not all

    equivalent) ways, but the definitions that yield the most significant consequences are

    given by [1]:

    The zeros of a transfer function matrix ( )H s , are the roots of the (nonzero) numerator

    polynomials ( ){ }i s in the Smith-McMillan form of ( )H s . The Smith-McMillan form

    allows us to give a physical interpretation of the zeros. If Zs is a zero, then the Smith-McMillan form of ( )H s will lose rank at Zs s= .

    The poles of a transfer function matrix ( )H s , are the roots of the denominator

    polynomials in the Smith-McMillan form of ( )H s .

    1.2.1.1 Smith McMillan Transformation

    Given a rational matrix ( )H s

    ( ) ( )

    ( )

    N sH s

    d s

    =

    where ( )d s is the monic least common multiple of the denominators of ( )H s

    Then ( ) ( ) ( )d s H s N s= is a polynomial matrix, so that we can write,

    ( ) ( ) ( ) ( ) ( ) ( )1 2d s H s N s U s s U s= =

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    where the ( ){ }iU s are unimodular matrices and ( )s is in Smith form

    ( ) ( ) ( ) ( )

    ( )

    ( )

    ( )

    ( )

    ( )

    ( )

    ( )

    1 1

    1 2

    i

    i i

    i

    s sU s H s U s diag

    d s d s

    s s

    d s s

    = =

    =

    where ( ) ( ){ },i is s are coprime, 1, ,i r=

    and r is the (normal) rank of ( )H s

    Then we can write

    ( ) ( ) ( ) ( )1 2H s U s M s U s=

    where ( )M s is the Smith-McMillan transformation of ( )H s given by

    ( )

    ( )

    ( )0

    0 0

    i

    i

    sdiag

    M s s

    =

    Smith Form

    For any p m polynomial matrix ( )P s we can find elementary row and column

    operations, or corresponding unimodular matrices ( ) ( ){ },U s V s such that

    ( ) ( ) ( ) ( )U s P s V s s=

    where

    ( )

    ( )

    ( )

    ( )

    0

    0

    0 0 0

    the (normal) rank of

    i

    r

    s

    ss

    r P s

    =

    =

    and the ( ){ }i s are unique monic polynomials obeying a division property

    ( ) ( )1 , 1, , 1i is s i r + =

    Moreover, if( ) ( )the gcd of all minors ofi s i i P s =

    then

    ( ) ( )

    ( ) ( )0

    1

    , 1i

    i

    i

    ss s

    s

    = =

    The matrix ( )s is called the Smith form of ( )P s

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    Example.1.2.1.1 [1] pp. 444-446

    Find the poles and zeros of

    ( )( ) ( )

    ( )

    ( ) ( )

    2

    2 2 2 2

    11

    1 2 1 1

    s s sG s

    s s s s s s

    + = + + + +

    SolutionGiven

    ( )( )

    ( )1

    G s N sd s

    =

    where

    ( ) ( ) ( ){ } ( ) ( )

    ( )

    ( )

    ( ) ( )

    2 2 2 2

    2

    2 2

    1 2 1 2

    1

    1 1

    d s lcm s s s s

    s s s

    N s s s s s

    = + + = + +

    +

    = + +

    Finding ( )s in Smith form:

    ( )

    ( ) ( ) ( ) ( )( )

    ( ) ( ) ( )( )( ) ( )

    ( ) ( ) ( ) ( )

    0

    2 2 2

    1

    23

    2

    1 1

    22

    2 2

    1

    gcd , 1 , 1 , 1

    gcd 1 2

    1 2

    s

    s s s s s s s s s

    s s s s

    s s s

    s s s s s

    =

    = + + + =

    = + +

    = =

    = = + +

    Therefore

    ( )

    ( )

    ( ) ( ) ( )

    2 2

    2

    00 1 2

    00 02

    i

    i

    ss

    diag s sM s s

    s

    s

    + + = =

    +

    The poles are defined as

    ( ) ( ) ( ) ( ) ( ) ( )[ ]

    2 2

    1 2 1 2 2 0

    1 1 2 2 2

    p s s s s s s

    p

    = = + + + ==

    The zeros are defined as

    ( ) ( ) ( )

    [ ]

    3

    1 2 0

    0 0 0

    z s s s s

    z

    = = =

    =

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    1.2.2 Stability of MIMO Systems

    Having defined a tool in order to obtain the poles and zeros of a MIMO system, its

    necessary to define if the system is stable. This can be achieved by the generalized

    Nyquists stability criterion, which is an adaptation from the Nyquists stability criterion

    for SISO systems.

    1.2.2.1 Generalized Nyquists Stability Criterion

    Let ( )G s be a rational TFM, assuming that it has no cancellations between poles and

    zeros. Let Kbe a compensator with a negative feedback loop, that is

    I ;K k k=

    Let the ( )det I KG s+ have P poles and Zzeros in the right hand plane (RHP), then

    like in SISO systems

    ( ) ( )arg det I 2KG s Z P + =

    where arg is the change of phase given by salong the Nyquists contour. In order to

    obtain stability in a closed loop, it is required that the diagram mapped by

    ( )det I KG s+

    surrounds the origin Ptimes.

    As a difference from the SISO case, the Nyquist diagram of each kof interest must be

    obtained.

    If ( )i s is an eigenvalue of ( )G s , then ( )ik s is an eigenvalue of ( )KG s , and

    therefore, ( )1 ik s+ is an eigenvalue of ( )I KG s+ . Then

    ( ) ( )det I 1 ii

    KG s k s+ = +

    and

    ( ) ( )arg det I arg 1 ii

    KG s k s + = +

    Therefore, the stability in a closed loop system can be inferred by the number of wind

    ups to the point ( )1,0 given by the Nyquist diagram of ( )ik s . The Nyquist diagram

    of ( )i s are known as the characteristic graphs of ( )G s .

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    Theorem If ( )G s has right hand plane poles (RHPP), P, given by the Smith-McMillan

    transformation, then the closed loop with negative feedback is stable if and only if the

    characteristic graphs of ( )KG s surround the point ( )1,0 P times in a counter-

    clockwise direction, assuming that there was no cancellations of instabilities.

    Example 1.2.2.1 [2] pp. 61Find the values of 0k> in order to keep ( )G s from becoming unstable

    ( )( )( )

    11

    6 21.25 1 2

    s sG s

    ss s

    =

    + +

    Solution

    Its easy to verify that the open loop poles of ( )G s are [ ]1 2P = , therefore, in

    order to maintain the closed loop system stable, we must ensure that the number of

    surroundings of the characteristic graphs of ( )G s is equal to zero.Assuming 1k= , then

    ( )

    ( )( )

    ( )( )

    2

    1

    2

    2

    det I 0

    2 2 3 24 1

    5 3 2

    2 2 3 24 1

    5 3 2

    KG s

    s s

    s s

    s s

    s s

    = =

    + + + + = = + + +

    From the eigenvalues of ( )G s , its possible to obtain the Generalized Nyquist Diagramwhen 1k =

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    From the diagram its possible to obtain the critical points in which we can calculate the

    values of k, in order to keep the system stable. Knowing that the critical points are in

    0.8 and 0.4 , therefore

    1 11.25 , 2.5

    0.8 0.4k k

    < = > =

    This can be proven by setting the values of kequal to 1.25 and 2.5 and obtaining the

    Nyquist Diagram.

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    1.2.3 Treating a MIMO system with SISO techniques

    1.2.3.1 Coupling degree and pairing of inputs and outputs

    Given the coupling degree of a MIMO system, its possible to apply certain SISO

    techniques for designing controllers. The degree of coupling can be found by several

    techniques, such as the Nyquists arrays and the Gershgorin bands, the relative gain

    array (RGA), and the individual channel design (ICD). In some cases, it is possible tocross couple inputs and outputs in order to obtain a less coupled system.

    1.2.3.2 Nyquists Arrays and Gershgorin bands

    The Nyquists array of a TFM ( )G s , is an array of graphs, where the i, j-est graph is the

    Nyquist Diagram of ,i jg .

    Gershgorin Theorem let Z a n n complex matrix. Then, the eigenvalues of Z fall

    on the union of circles with center at,i i

    z with radius

    ,1

    m

    i jj

    j i

    Z=

    and on the circles with center at,j j

    z with radius

    ,1

    m

    i ji

    i j

    Z=

    Gershgorin Bands

    Over the Nyquists diagram of ( ),i ig s , on each point, we super impose a circle of

    radius

    ( ) ( ), ,1 1

    orm m

    i j j ii i

    i j i j

    g j g j = =

    The bands obtained in this way are known as the Gershgorin Bands.

    By the Gershgorin theorem its possible to know that the bands trap the unions of theNyquist diagram. More over, its possible to demonstrate that the bands occupy

    different regions, therefore there will be as many Nyquists diagrams trapped in a region

    as many Gershgorin bands are there.

    Then, by counting the number of wind ups that the Gershgorin bands do around the

    point ( )1,0 , its possible to determine the stability of the MIMO system.

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    If the Gershgorin bands are thin and exclude the origin, it is said that ( )G s is

    diagonally dominant which can be interpreted as a decoupled system.

    Example 1.2.3.1 [3] pp. 657

    Find the Gershgorin bands of

    ( )2

    2 2

    2 0.1

    13 2

    0.1 6

    2 1 5 6

    ss sG s

    s s s s

    ++ +

    = + + + +

    From the graphs above, its possible to observe that the system is stable and highly

    decoupled. Therefore, it can be managed as two independent SISO systems with small

    disturbances due to the small coupling degree.

    1.2.3.3 Relative Gain Array (RGA)

    To measure the degree of coupling or interaction in a system, the concept of relative

    gain array can be used. For an arbitrary n n matrix A, it is defined as

    ( ) ( )1RGA .*T

    A A A=

    The RGA matrix has a number of interesting properties

    The sum of the elements of any row or column is always 1 RGA is independent of any scaling

    The sum of the absolute values of all elements in ( )RGA A is a good measure of

    As true condition number, i.e., the best condition number that can be achieved

    in the family 1 2D AD , where iD are diagonal matrices.

    Permutation of the rows or columns of A leads to permutations of the

    corresponding rows or columns of ( )RGA A .

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    ( )

    ( )

    12 21

    11 22

    1

    i ii

    i

    i ii

    g gs

    g g

    k gh s

    k g

    =

    =+

    The MSF ( )s is of great importance inside the ICD analysis framework, since it is

    capable of [6]

    Determining the dynamical characteristics between each input and each output

    It has an interpretation in the frequency domain

    Its magnitude quantifies the amount of coupling between the channels

    It can determine the transmittance zeros of the system from ( )1 s

    ( ) 1s = determines the non-minimum phase conditions

    Its closeness to the point ( )1,0 its a key point in determining the robustness ofthe system

    Robustness Conditions

    In order to obtain a design that provides a channel that is robust and stable, the

    following conditions should be satisfied

    1. ( )s should not be close to the point ( )1,0 for all

    2. ( ) ( )is h s shall be robust

    3. ( ) ( )i iik s g s shall be robust

    The interaction between the discarded inputs and outputs can be observed from

    ( ) ( )

    ( ) ( )

    ( ) ( )

    1

    1

    ij

    i j j

    jj i

    g sY s h s R s

    g s C s=

    +

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    2. Function Reference

    The aim of this chapter is to give a brief description of the functions used in the MIMO

    toolbox. For the users that are new to the Matlab environment it is recommended to

    review the getting started documentation.

    2.1 The Symbolic Transfer Function

    The Control Toolbox in Matlab posses an object class that describes a transfer function.

    This model representation is numerical and its sensitive to floating point errors due to

    arithmetic operations such as inversion. Also, from the LTI definition, the transfer

    function class cannot handle nonlinearities such as square roots, trigonometric

    functions, etc, since its only a rate in polynomial representation. Given such problems,

    a symbolic conversion for transfer function has been developed, and its key to some of

    the functions inside the MIMO toolbox. This conversion enables the user to handle the

    transfer function and its operations as an algebraic problem, simplifying the

    computational difficulties that may arise for the users without a computer sciencebackground.

    2.2 Function Description

    2.2.1 tf2sym

    SyntaxG_sym = tf2sym(G)

    Description

    tf2sym performs the conversion from a numeric to a symbolic representation of atransfer function. The function is capable to deal with both SISO and MIMO models.

    To be able to differentiate the type of transfer function, the symbolic transfer function is

    represented with the Laplace operator p instead of s.

    Example 1>> G=tf([1 2 3],[1 5 6 7])

    >> G_sym=tf2sym(G);

    >> pretty(G_sym)

    2

    3 + p + 2 p

    -------------------

    3 2p + 5 p + 6 p + 7

    Example 2>> g11=tf([1 2],[1 2 1]);

    g12=tf([1 -1],[1 5 6]);

    g21=tf([1 -1],[1 3 2]);

    g22=tf([1 2],[1 1]);

    G=[g11 g12; g21 g22];

    g=tf2sym(G);

    pretty(g)

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    [ 2 + p -1 + p ]

    [ -------- ---------------]

    [ 2 (p + 3) (2 + p)]

    [ (p + 1) ]

    [ ]

    [ -1 + p 2 + p ]

    [--------------- ----- ]

    [(2 + p) (p + 1) p + 1 ]

    2.2.2 sym2tf

    SyntaxG = sym2tf(G_sym)

    Description

    sym2tf performs the conversion from a symbolic to a numeric representation of a

    transfer function. As tf2sym, this function is capable of dealing with both SISO and

    MIMO models. This conversion cannot handle nonlinearities since the numeric transfer

    function class tf is not capable of dealing with the nonlinearities.

    Example 1>> syms p

    >> G_sym = (p^2 + 2*p + 3)/(p^3 + 5*p^2 + 6*p + 7);

    >> G=sym2tf(G_sym)

    Transfer function:

    s^2 + 2 s + 3

    ---------------------

    s^3 + 5 s^2 + 6 s + 7

    Example 2>> g11=(p + 2)/(p^2 + 2*p + 1);

    g12=(p - 1)/(p^2 + 5*p + 6);

    g21=(p - 1)/(p^2 + 3*p + 2);

    g22=(p + 2)/(p + 1);

    g=[g11 g12; g21 g22];

    G=sym2tf(g)

    Transfer function from input 1 to output...

    s + 2

    #1: -------------

    s^2 + 2 s + 1

    s - 1

    #2: -------------

    s^2 + 3 s + 2

    Transfer function from input 2 to output...s - 1

    #1: -------------

    s^2 + 5 s + 6

    s + 2

    #2: -----

    s + 1

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    2.2.3 ss2sym

    SyntaxG = ss2sym(A,B,C,D)

    Description

    ss2symperforms the conversion from a state space representation to a symbolic transfer

    function.

    Example>> A = [0 1 0 0 0; 0 0 1 0 0; -2 -5 -4 0 0; 0 0 0 0 1; 0 0 0 -3 -4];

    B = [0 0; 0 0; 1 0; 0 0; 0 1];

    C = [1 2 1 9 3; 14 9 1 1 1];

    D = [0 1; 0 0];

    g=ss2sym(A,B,C,D);

    pretty(g)

    [ 1 p + 4]

    [ ----- -----]

    [ 2 + p p + 1]

    [ ][ p + 7 1 ]

    [-------- -----]

    [ 2 p + 3]

    [(p + 1) ]

    2.2.4 smform

    Syntax[M,poles,zeros] = smform(G)

    Description

    [M,poles,zeros] = smformcomputes the Smith-McMillan transformation, the poles

    and zeros of a MIMO TFM. The algorithm obeys directly the theory specified on thesection 1.2.2.1 of this document by establishing an active link with the Maple kernel.

    Example>> g11=tf([1 1],[1 3 2]);

    g12=tf([1 4],[1 1]);

    g21=tf([1 7],[1 2 1]);

    g22=tf([1 2],[1 5 6]);

    G=[g11 g12 ; g21 g22];

    [M,poles,zeros]=smform(G);

    >> pretty(M)

    [ 1 ]

    [------------------------ 0 ]

    [ 2 ]

    [(p + 3) (p + 1) (2 + p) ]

    [ ]

    [ 4 3 2 ]

    [ p + 15 p + 86 p + 203 p + 167]

    [ 0 --------------------------------]

    [ p + 1 ]

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    >> poles

    poles =

    -3.0000

    -2.0000

    -1.0000

    -1.0000 + 0.0000i

    -1.0000 - 0.0000i

    >> zeros

    zeros =

    -5.3101 + 2.5439i

    -5.3101 - 2.5439i

    -2.1899 + 0.1460i

    -2.1899 - 0.1460i

    2.2.5 rga

    SyntaxA=rga(G)

    Description

    rgacomputes the Relative Gain Array of a MIMO TFM. The algorithm obeys directly

    the theory specified on the section 1.2.3.3

    Example>> g11=tf([1 2],[1 2 1]);

    g12=tf([1 -1],[1 5 6]);

    g21=tf([1 -1],[1 3 2]);

    g22=tf([1 2],[1 1]);

    G=[g11 g12; g21 g22];

    A=rga(G)

    A =

    1.0213 -0.0213

    -0.0213 1.0213

    2.2.6 nyqmimo

    Syntaxnyqmimo(G)

    Description

    nyqmimocomputes the Nyquists Diagram based on the type of transfer function at theinput. nyqmimodistinguishes between transfer functions with singularities at the origin,

    proper, strictly proper and strictly improper transfer functions, based on that structure, it

    maps the Nyquists Diagram according to the Nyquists Contour. nyqmimo is capable

    of computing the Nyquists Diagram for SISO and the Generalized Nyquists Diagram

    for MIMO systems.

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    Example 1>> G=tf([1 25],[1 5 3 -9 0]);

    nyqmimo(G)

    Example 2

    >> den=1.25*conv([1 1],[1 2]);g11=tf([1 -1],den);

    g12=tf([1 0],den);

    g21=tf([-6],den);

    g22=tf([1 -2],den);

    G=[g11 g12;g21 g22];

    nyqmimo(G)

    2.2.7 m_circles

    Syntaxm_circles

    Description

    m_circlessuperimposes the M circles of magnitude -2dB to 20dB. This function is

    useful to measure the gain margin on a Nyquists Diagram.

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    Example>> G=tf(1,[1 2 1]);

    >> nyqmimo(G)

    Verifying for sigularities on the origin...

    Setting frequency range...

    Mapping...

    Plotting...

    >> m_circles

    2.2.8 icdtool

    Syntaxicdtool(G)

    Descriptionicdtool is a GUI designed to help the user in the task of designing controllers for a

    2 2 MIMO system with under the Individual Channel

    Design Scheme.

    By default, icdtool calculates ( )s , when just loaded, icdtool will not load the

    default controller. The controller will only be loaded and all the proper calculations

    performed after the user has clicked on the UPDATE CONTROLLERS button. If the

    user doesnt know entirely the behavior of the system, it is recommended that they load

    a unitary gain proportional controller, in that way, the user will be able to analyze both,

    ( )s and the diagonal elements of the system, ( ) ( )1,1 2,2,g s g s . It is possible to load a

    proportional controller by clearing the poles and zeros entries.

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    2.2.9 gershband

    Syntaxgershband(G) Gershgorin bands of G

    gershband(G,v) Gershgorin bands and Nyquist Array of G

    Description

    gershbandcomputes the Gershgorin Bands of a n n MIMO system along with the

    Nyquists Array.

    Example>> g11=tf([1 2],[1 2 1]); g12=tf([1 -1],[1 5 6]);

    g21=tf([1 -1],[1 3 2]); g22=tf([1 2],[1 1]);

    G=[g11 g12; g21 g22];

    gershband(G,v);

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    2.2.10 arrowh

    SyntaxArrowh(x,y,color,size,location)

    Description

    arrowhdraws a solid arrowhead in the current plot

    Author: Florian Knorn

    Email: [email protected], [email protected]

    Homepage: http://www.florian-knorn.com/

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    3. References

    [1] Kailath, Thomas, Linear Systems, Prentice Hall, 1980, pp. 390-392, 443-450[2] Maciejowski, J.M., Multivariable Feedback Design, Addison-Wesley, 1989,

    pp. 37-71

    [3] Goodwin, Graham C., Graebe, Stefan F., Salgado, Mario E., Control System

    Design, Prentice Hall, 2001, pp. 653-671

    [4] Nise, Norman S., Sistemas de Control para Ingeniera, CECSA, 2002, pp. 614-

    635

    [5] Ogata, Katsuhiko, Ingeniera de Control Moderna, Prentice-Hall, 2003, 523-

    566

    [6] Carlos E. Ugalde-Loo, Eduardo Licaga-Castro, Jess Licaga-Castro, 2x2

    Individual Channel Design MATLAB Toolbox Proceedings of the 44th IEEE

    CDC, pp. 7603-7608

    [7] J. Liceaga, E. Liceaga and L. Amzquita, Multivariable Gyroscope Control byIndividual Channel Design, Control Systems Society CCA, pp. 110-115, 2005

    [8] E, Liceaga-Castro and J. Liceaga-Castro, Submarine depth control by

    individual channel design, Proceedings of the 37th

    IEEE CDC, e, pp. 3183-

    3188, 1998

    [9] J. Licaga-Castro, C. Ramrez-Espaa and E. Licaga-Castro, GPC control

    design for a Temperature and Humidity Prototype using ICD anlisis,

    Submitted for publication.